It's an absolute disaster for one. I haven't actually managed to get shared folders to work reliably in years. It ended up being faster and more reliable to run Samba on the host and connect over a virtual network.

Some of the other features of course can't easily be duplicated with other tools and they work decent-ish anyways so there's no reason to try, but shared folders aren't one of them.

You might not want to be locked in. I've used VirtualBox to build systems meant to eventually run elsewhere.